1. Field of the Invention
The present invention relates to a rechargeable battery. In particular, the present invention relates to a structure that couples an external terminal of a cap assembly and an electrode assembly that are mounted inside a battery container.
2. Description of the Related Art
High-power rechargeable batteries for environmentally friendly motor vehicles and for slim and portable electronic devices have recently been developed. Non-aqueous electrolyte rechargeable batteries are often used in these applications. The positive plate and the negative plate of a non-aqueous electrolyte rechargeable battery generally comprise an alkaline metal such as lithium, and the container for the rechargeable battery is sealed so as to prevent the alkaline metal from reacting with moisture from the air.
A sealed rechargeable battery includes a container that has an opening at its upper end and an electrode assembly mounted inside the container that is immersed in an electrolyte. It also includes an external terminal fixed to the container to seal the battery, such as by a cap assembly with a positive terminal. A positive plate of the electrode assembly is connected to the cap assembly through a tab.
A rechargeable battery of the type mentioned above that connects the electrode assembly to the external terminal using only a single tab increases internal resistance when carrying the voltage generated from each region of the electrode assembly to the external terminal. Accordingly, it cannot transfer the current of the electrode assembly to the external terminal enough to maximize the battery characteristics. This makes this type of rechargeable battery unsuitable for use in high power motor-driven devices.
Furthermore, this type of rechargeable battery does not uniformly extract the voltage generated from each region of the electrode assembly. This causes voltage differences between a region where the electrode assembly is welded to the tab and other regions that are at a distance from the tab. Such a voltage difference increases the deterioration of the welded portion as charge and discharge steps are repeated, and also results in reduced power and lifespan of the battery. Such problems are especially serious in a battery for a motor-driven device which repeats the charge and discharge within a short time.